What feeling dizziness during exercise means – by MD Thordis Berger

Commonly, it is the result of dehydration and improper breathing techniques or low blood sugar.

Dehydration

Dehydration occurs when the body loses too much fluid and can't adequately replace it.
With any form of exercise, fluid will be lost from sweating, however in moderate to intense physical activity, the fluid loss will be much greater. In addition to losing water, the body sweats out electrolytes, particularly sodium, that helps maintain water balance.
A general rule is to drink when you are thirsty, which many athletes don't do.
Finally, keep in mind that hydration effects muscle growth, recovery and weight loss in a big way.

Improper Breathing

Smooth and efficient breathing is crucial for delivering the oxygen our bodies need to perform functions properly. Proper breathing can also help athletes exercise longer with less effort, and even calm the mind.
If you are overexerting yourself or are not used to exercising, your breathing may be too superficial and/ or too rapid. This can lead to dizziness, weakness or the feeling that you are going to faint.
Different activities require different breathing techniques. Consult a trainer certified in your field of activity for recommendations on proper breathing techniques.

Low Blood Sugar

Sugar in the form of glucose is the fuel that our body needs for most of its functions. If you don't get enough to eat, your body will not have enough glucose, a condition referred to as hypoglycemia.
If you are exercising without eating enough, your blood sugar will usually be low, which can lead to dizziness. Other symptoms, such as nausea, increased heart rate and trembling may also occur. Eating at least two to four hours before exercising can help avoid low blood sugar.

Warning

If you experience dizziness during exercise, stop whatever you are doing and rest. Keep your head above your heart. If the dizziness does not respond to drinking fluids or eating something and does not go away after an hour, contact a doctor.
Seek immediate medical attention if you have dizziness along with one or more of the following symptoms: chest pain, heart palpitations, shortness of breath, weakness, inability to move an arm or leg or a change in vision or speech